Since GTAIII, NPC's do fly aircraft in some missions plus when you have 3 or more stars, and there's the air traffic in SA too. Although they don't usually do fancy flying like that bit of the trailer.

What I am actually saying, you never see an NPC sitting inside the cockpit, when the Police chopper or the Hydra comes on your tail. The cockpit is genuinely blank, it's the game that operates them by itself. Related thread